This test checks the performance benefits of CSS-Contain on a spreadsheet like situation.
The page contains 10,000 auto-sized DOM nodes,
placed in a 100 column grid with auto sized columns.
Clicking "Update" replaces the content of the textNode of each DOM node with a random number.
This requires a full relayout.
Making the nodes fixed size and applying contain:strict
should make an update go significantly faster,
since a full relayout should not be necessary.
Just to be sure this isn't triggering anything grid specific,
you can turn off grid, and be left with 10,000 inline-blocks.
The same logic should apply.